With regard to mesh itself, the larger the number of holes per inch, the smaller each hole must be. And the smaller the hole, the smaller an item must be in order to pass through such mesh. So for a mesh number: bigger numbers equals smaller holes, basically.
If you look at the drop down selector for "Cube Size", there are six sizes listed. The first two listings involve sizes I believe are larger than literal gold dust, being more akin to small nuggets rather than dust. I’ve included these two larger sizes in order to better depict how quickly value changes from size to size. The literal gold dust mesh categories follow beneath these first two. Because there are many particle sizes that qualify as gold dust, or flour gold, I arbitrarily chose four that I believe represent dust reasonably well: 35 mesh (0.50 mm), 60 mesh (0.25 mm), 120 mesh (0.12 mm), and 230 mesh (0.06 mm), this last one being about the width of a human hair.
Notice that each of these mesh categories is roughly double the one prior, while the millimeter measure on each are halved. So there is a factor of two with regard to the length of a side (sidewall dimension) between categories. Since volume is figured by cubing a sidewall dimension, we end up with each volume being eight times different than the last: two cubed is eight. Therefore, from the sizes I provide, you can get an idea of what happens to value for sizes not shown. Mesh is merely a label. It is specifically the length in millimeters that gets cubed.